Receive the latest national-international updates in your inbox

It's customary to leave a tip when eating out, but one particular gratuity added to an order for a milkshake and fries at a New Jersey diner is angering parents.

"My daughter was coming to me, telling me that every time she and her friends went to the diner, they're being charged the gratuity," said Melissa Desch. "And when I asked her why, she said, 'Because they're children.'"

Desch said her daughter Isabella and other students at the Colfax Schuyler Middle School frequently go to the Wayne Hills Diner, just across the Hamburg Turnpike from the school. The diner's policy of adding the tip applies to kids only, and Desch believes that's unfair.

"I was always told servers were always paid upon their service," she said.

Peter Logos, one of the diner's owners, defended the policy, saying that the establishment is hit with large numbers of kids at a time, especially on Fridays. That ties up waitstaff, who aren't often tipped.

He said the menu clearly states the diner will add an 18-percent gratuity at its discretion.

Some Wayne High School students said they first noticed the addition to their bills around the time football season started -- and did not mind.

"It's not about the establishment," Desch said. "I've been going there since I was a child. But with them, they don't understand and they just pay the bill, And you know, she doesn't understand that she has a right to not pay a tip."